Widespread evidence suggests that a unifying principle governing the molecular pathology of cancer is the co-dependent aberrant regulation of core machinery driving proliferation and suppressing apoptosis. Anomalous proteins engaged to support a tumorigenic regulatory environment likely represent optimal intervention targets in a heterogenous population of cancer cells. The advent of RNAi-based functional genomics provides the opportunity to derive unbiased comprehensive collections of validated gene targets supporting critical biological systems outside the framework of preconceived notions of mechanistic relationships. Here, I have combined a high throughput cell-based one-well/one-gene screening platform with an arrayed genome-wide synthetic siRNA library for systematic interrogation of the molecular underpinnings of cancer cell chemoresponsiveness. NCI-H1155, a human non small cell lung cancer line, was employed for a paclitaxel-dependent synthetic lethal screen designed to identify gene targets that specifically reduce cell viability in the presence of otherwise suboptimal pactlitaxel concentrations. Using a stringent objective statistical algorithm to reduce false discovery rates below 5%, we isolated a panel of 87 genes that represent major fulcrums of the cancer cell autonomous response to abrogation of microtubule dynamics. Importantly, a number of these targets sensitize lung cancer cells to paclitaxel concentrations 1000-fold lower than otherwise required for a significant response, and reveal novel mechanistic relationships between cancer-associated aberrant gene expression programs and the basic cellular machinery required for robust mitotic progression. In the studies proposed herein, I plan to characterize the mechanism of action of these targets and determine if they are required for tumor cell survival and chemoresistance in vivo. My specific aims are to 1: Defining the contribution of novel paclitaxel sensitizers to cancer cell spindle assembly and function. 2: Validate effectiveness of candidate therapeutic targets with orthotopic xenograft models of lung cancer. 3: Isolate the core components of the cancer cell network that liberate chemoresistant tumors from mitotic catastrophe checkpoints. With respect to public health, these studies will aid in identifying both novel chemotherapeutics as well as novel combinations of existing chemotherapeutics to better treat cancer.